Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor workpiece, wafer, or substrate, and patterning the various material layers using lithography. The material layers typically comprise thin films of conductive, semiconductive, and insulating materials that are patterned, etched, or altered to form integrated circuits (ICs). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip, for example.
Many ICs include on-chip electrostatic discharge (ESD) protection circuits designed to protect the ICs against ESD surges. An ESD protection circuit typically is designed to turn on during an ESD event and form a current discharge path to shunt the large ESD current and clamp the voltage of input/output (I/O) and supply pads to a sufficiently low level to prevent the IC from being damaged. The current shunting path is often provided by an active device that provides an active path with a relatively low on-resistance, for example. An ESD protection circuit typically ensures a low ohmic path to prevent voltages from building up to potentially damaging levels.
ESD protection circuits may include elements such as diodes, resistors, thyristors, transistors, and/or capacitors, as examples. A typical ESD protection circuit may include a trigger circuit, a buffer circuit, and/or a clamping circuit, as examples.
Some components or portions of ESD protection circuits may be large and may require a large amount of area on an integrated circuit. As some devices on ICs such as logic circuitry, memory, and other circuitry are scaled to smaller geometries, the size of ESD protection circuits may not necessarily decrease in size. ESD protection circuits may occupy a large percentage of the surface area of die and may limit further reduction in size of an IC. ESD protection circuits usually occupy a significant portion of the pad or chip area; therefore, reducing ESD protection circuit area would have a significant impact on the total pad area and ultimately, on the total chip area.
Thus, what are needed in the art are more area-efficient methods of providing on-chip ESD protection in semiconductor devices and structures thereof.